scholarly journals Interaction Energy Analysis of Monovalent Inorganic Anions in Bulk Water Versus Air/Water Interface

Molecules ◽  
2021 ◽  
Vol 26 (21) ◽  
pp. 6719
Author(s):  
John M. Herbert ◽  
Suranjan K. Paul
Keyword(s):  
Surface Activity ◽  
Mechanical Energy ◽  
Decomposition Analysis ◽  
Bulk Water ◽  
Active Species ◽  
Energy Decomposition Analysis ◽  
Water Interface ◽  
Surface Activities ◽  
Air Water Interface ◽  
Surface Active

Soft anions exhibit surface activity at the air/water interface that can be probed using surface-sensitive vibrational spectroscopy, but the structural implications of this surface activity remain a matter of debate. Here, we examine the nature of anion–water interactions at the air/water interface using a combination of molecular dynamics simulations and quantum-mechanical energy decomposition analysis based on symmetry-adapted perturbation theory. Results are presented for a set of monovalent anions, including Cl−, Br−, I−, CN−, OCN−, SCN−, NO2−, NO3−, and ClOn− (n=1,2,3,4), several of which are archetypal examples of surface-active species. In all cases, we find that average anion–water interaction energies are systematically larger in bulk water although the difference (with respect to the same quantity computed in the interfacial environment) is well within the magnitude of the instantaneous fluctuations. Specifically for the surface-active species Br−(aq), I−(aq), ClO4−(aq), and SCN−(aq), and also for ClO−(aq), the charge-transfer (CT) energy is found to be larger at the interface than it is in bulk water, by an amount that is greater than the standard deviation of the fluctuations. The Cl−(aq) ion has a slightly larger CT energy at the interface, but NO3−(aq) does not; these two species are borderline cases where consensus is lacking regarding their surface activity. However, CT stabilization amounts to <20% of the total induction energy for each of the ions considered here, and CT-free polarization energies are systematically larger in bulk water in all cases. As such, the role of these effects in the surface activity of soft anions remains unclear. This analysis complements our recent work suggesting that the short-range solvation structure around these ions is scarcely different at the air/water interface from what it is in bulk water. Together, these observations suggest that changes in first-shell hydration structure around soft anions cannot explain observed surface activities.

scholarly journals Interaction Energy Analysis of Monovalent Inorganic Anions in Bulk Water Versus Air/Water Interface

2021 ◽  
Author(s):  
John Herbert ◽  
Suranjan Paul
Keyword(s):  
Interaction Energy ◽  
Surface Activity ◽  
Mechanical Energy ◽  
Decomposition Analysis ◽  
Bulk Water ◽  
Active Species ◽  
Energy Decomposition Analysis ◽  
Water Interface ◽  
Air Water Interface ◽  
Surface Active

Soft anions exhibit surface activity at the air/water interface that can be probed using surface-sensitive vibrational spectroscopy, yet the statistical mechanics behind this surface activity remains a matter of debate. Here, we examine the nature of anion--water interactions at the air/water interface using a combination of molecular dynamics simulations and quantum-mechanical energy decomposition analysis based on symmetry-adapted perturbation theory. Results are presented for a set of monovalent anions including Cl–, Br–, I–, CN–, OCN–, SCN–, NO2–, NO3–, and ClOn– (n = 1, 2, 3, 4), several of which are archetypal examples of surface-active ions. In all cases, we find that anion–water interaction energies are systematically larger in bulk water although the difference (with respect to the interaction energy in the interfacial environment) is well within the magnitude of the instantaneous fluctuations. Specifically for the surface-active species Br–(aq), I–(aq), ClO4–(aq), and SCN–(aq), and also for ClO–(aq), the charge-transfer (CT) energy is found to be slightly larger at the interface than it is in bulk water, but in all cases the CT stabilization amounts to < 20% of the total induction energy. CT-free polarization energies are systematically larger in bulk water, for all of the ions. This analysis complements our recent work suggesting that the short-range solvation structure around these ions is scarcely different at the air/water interface from what it is in bulk water. Together, these observations suggest that changes in first-shell hydration structure around soft anions cannot explain observed surface activities.

Surface-active spore slimes

1975 ◽  
Vol 53 (21) ◽  
pp. 2543-2546 ◽  
Author(s):  
R. J. Bandoni
Keyword(s):  
Surface Activity ◽  
Bulk Phase ◽  
Water Interface ◽  
Spore Dispersal ◽  
Air Water Interface ◽  
Surface Active

Twenty-four species of fungi with slimy spore masses were examined for surface activity of the slime. The species fell into four categories: (1) slime highly surface-active and spores dispersed primarily at the air-water interface; (2) slime rapidly spreading in the bulk phase and the spores spread throughout; (3) slime weakly spreading or insoluble in water; (4) slime insoluble in water, but showing some activity in oil or lactophenol solution. The significance of this activity with respect to spore dispersal is discussed.

Surface active properties at the air–water interface of β-casein and its fragments derived by plasmin proteolysis

1989 ◽  
Vol 56 (3) ◽  
pp. 487-494 ◽  
Author(s):  
Michael Wilson ◽  
Daniel M. Mulvihill ◽  
William J. Donnelly ◽  
Brian P. Gill
Keyword(s):  
Surface Tension ◽  
Water Interface ◽  
Active Protein ◽  
Drop Volume ◽  
V Protein ◽  
Proteose Peptone ◽  
Rate Determining Step ◽  
Surface Active Properties ◽  
Air Water Interface ◽  
Surface Active

Summaryβ-Casein, was enzymically modified by incubation with plasmin to yield γ-caseins and proteose peptones. Whole γ-, γ1-, γ2/γ3-caseins and whole proteose peptone (pp) were isolated from the hydrolysate mixture. The time dependence of surface tension at the air-water interface of solutions of β-casein and its plasmin derived fragments, at concentrations of 10−1 to 10−4% (w/v) protein, pH 7.0, was determined, at 25 °C, using a drop volume apparatus. The ranking of the proteins with respect to rate of reduction of surface tension, during the first rate determining step, at 10-2% (w/v) protein, was γ2/γ3 ≫ pp > whole γ- > γ1- > β-casein. The ranking of the proteins with respect to surface pressures attained after 40 min (π40) was concentration dependent. γ2/γ3-Caseins were found to be very surface active, decreasing surface tension rapidly and giving a high π40. γ1 Casein decreased surface activity somewhat faster than β-casein, but generally reached a lower π40. Whole γ-casein reflected the properties of both γ1 and γ2/γ3-caseins. Proteose peptone was found to decrease surface tension rapidly during the initial rate determining step; it gave a relatively high π40 at a bulk phase concentration of 10−3% (w/v) protein, but, it was the least surface active protein at 10−1 and 10−2% (w/v) protein.

scholarly journals Aerosol microdroplets exhibit a stable pH gradient

2018 ◽  
Vol 115 (28) ◽  
pp. 7272-7277 ◽  
Author(s):  
Haoran Wei ◽  
Eric P. Vejerano ◽  
Weinan Leng ◽  
Qishen Huang ◽  
Marjorie R. Willner ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Bulk Water ◽  
Bulk Solution ◽  
Spatial Gradient ◽  
Water Interface ◽  
Atmospheric Reactions ◽  
Air Water Interface ◽  
Surface Enhanced Raman ◽  
Enhanced Raman Scattering ◽  
2D And 3D

Suspended aqueous aerosol droplets (<50 µm) are microreactors for many important atmospheric reactions. In droplets and other aquatic environments, pH is arguably the key parameter dictating chemical and biological processes. The nature of the droplet air/water interface has the potential to significantly alter droplet pH relative to bulk water. Historically, it has been challenging to measure the pH of individual droplets because of their inaccessibility to conventional pH probes. In this study, we scanned droplets containing 4-mercaptobenzoic acid–functionalized gold nanoparticle pH nanoprobes by 2D and 3D laser confocal Raman microscopy. Using surface-enhanced Raman scattering, we acquired the pH distribution inside approximately 20-µm-diameter phosphate-buffered aerosol droplets and found that the pH in the core of a droplet is higher than that of bulk solution by up to 3.6 pH units. This finding suggests the accumulation of protons at the air/water interface and is consistent with recent thermodynamic model results. The existence of this pH shift was corroborated by the observation that a catalytic reaction that occurs only under basic conditions (i.e., dimerization of 4-aminothiophenol to produce dimercaptoazobenzene) occurs within the high pH core of a droplet, but not in bulk solution. Our nanoparticle probe enables pH quantification through the cross-section of an aerosol droplet, revealing a spatial gradient that has implications for acid-base–catalyzed atmospheric chemistry.

Surface activity of perfluorodecanoyl end-capped poly(ethylene oxide) and associated adsorption behavior to the air–water interface

Polymer ◽  
1998 ◽  
Vol 39 (19) ◽  
pp. 4655-4664 ◽  
Author(s):  
Zhaohui Su ◽  
Thomas J McCarthy ◽  
Shaw ling Hsu ◽  
Howard D Stidham ◽  
Zhongyong Fan ◽  
...  
Keyword(s):  
Ethylene Oxide ◽  
Surface Activity ◽  
Adsorption Behavior ◽  
Water Interface ◽  
Air Water Interface ◽  
Poly Ethylene Oxide ◽  
Poly Ethylene
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